PT voltage question

[paul525715]

I have a Partridge transformer with the following specs...

Secondary #1: 450-20-0-20-450
Secondary #2: 3.15-0-3.15

Can I confirm that to get a lower B+, I can connect the 20-0-20 part of #1 together (to effectively make 430-0-430)?

Is there any way to get an even lower B+? If there is, please spell it out simply... I've never had to fiddle with PT voltages before.

Thanks!